docs: def variables(
              self,
              name=None,
              function=None,
              decl_type=None,
              header_dir=None,
              header_file=None,
              recursive=None,
              allow_empty=None):
  
          """returns a set of variable declarations, that are matched defined
          criteria"""
          return (
              self._find_multiple(
                  self._impl_matchers[
                      scopedef_t.variable],
                  name=name,
                  function=function,
                  decl_type=decl_type,
                  header_dir=header_dir,
                  header_file=header_file,
                  recursive=recursive,
                  allow_empty=allow_empty)
          )